1. Field of the Invention
The present invention relates to semiconductor light-emitting devices including semiconductor light-detecting elements for detecting emitted light, and particularly to a semiconductor light-emitting device suitable for high-optical-detection-accuracy applications.
2. Description of the Related Art
A semiconductor light-emitting device used in the related art for applications such as optical fibers and optical disks has a light-detecting mechanism for detecting light emitted from a semiconductor light-emitting element built into the light-emitting device to keep the optical output level thereof constant. The light-detecting mechanism includes, for example, a reflector configured to split off a portion of the emitted light and a semiconductor light-detecting element configured to detect the split light. This mechanism, however, has a problem in that the number of components is increased and that the reflector and the semiconductor light-detecting element are to be accurately positioned relative to the semiconductor light-emitting element. One possible solution to that problem is to integrally form the semiconductor light-emitting element and the semiconductor light-detecting element.
However, if the two elements are integrally formed, the semiconductor light-detecting element can detect not only stimulated emission light, which is to be detected, but also spontaneous emission light. In this case, the optical output level of the semiconductor light-emitting element measured on the basis of the light detected by the semiconductor light-detecting element would contain the error corresponding to the spontaneous emission light. Thus, this method is unsuitable for applications where the optical output level is to be accurately controlled.
Japanese Patent No. 2877785 proposes a technique of providing a control layer in the semiconductor light-detecting element to block a portion of spontaneous emission light input from the semiconductor light-emitting element before the light is detected by the semiconductor light-detecting element.